There has been developed a system for remotely controlling electrical loads distributed over a wide area (such as a large office building or factory) from a microprocessor based central controller. That system is disclosed in U.S. Pat. No. 4,367,414--Miller et al, issued Jan. 4, 1983. The information disclosed in that patent is incorporated by reference thereto as if fully set forth herein. In the Miller '414 system, control instructions are issued by the central controller 50 and are tarnsmitted to various transceiver-decoders 56 via a twisted pair cable 58 constituting a bidirectional communications channel. A particular transceiver-decoder that is "addressed" carriers out the command by actuating one or more particular relays to make or break an electrical connection as desired. The central controller issues its control instructions in accordance with a predetermined schedule, in response to a measured parameter (such as light level or temperature) or in response to a user switch actuation sensed by a switch processor in the transceiver decoder and transmitted to the central controller over the bi-directional communications link, or in response to a user command telephonically transmitted to the central controller.
Although the Miller '414 system operates effectively as disclosed, further enhancements are now possible. This patent is directed to improvements in the transceiver-decoder, particularly to a switch input arrangement for processing various binary closure inputs to the transceiver decoder to be transmitted to the central controller to give it information or request a relay state change.
The enhanced transceiver-decoder is configured in a modular fashion. Separate switch and relay "modules" are provided to allow a user of the product to configure a remote control panel to meet his specific application needs. This modular construction is field adaptable allowing an electrician who has no electronic expertise to easily install, replace and service the panels. To do this, small modules are developed so that they can be easily handled and configured in the field.
It is now possible to further enhance means for sensing the ON/OFF condition of binary contacts to make appropriate control decisions. In the system depicted in FIG. 1 of Miller '414, central controller 50 could interrogate binary inputs located on a remotely located transceiver and determine the proper control output needed in response to the condition of those binary sensors. This is particularly useful where a thermostat is employed as a binary input to the central controller which would turn ON and Off or cycle heating ventilation air conditioning systems according to the ON/OFF condition of the thermostat switch which would be preset to a predetermined temperature threshold. Additionally, a photo relay or switch can be connected to these binary inputs to determine which lights are to go ON and OFF within a perimeter office in response to the amount of sunlight entering the area.
It is desirable to be able to selectively disable the response to certain or specified individual switch inputs thereby allowing certain switch inputs to be masked out. As previously disclosed in Miller '414, the actuation (either opening or closing) of a contact causes immediate transmission back to the controller so that appropriate control information can be transmitted forcing the proper load state. It may be desired at certain times of day, however, to disable selected switches so that no action occurs ignoring its ON/OFF condition. A typical application would include night setback thermostats where two thermostats would be connected to two binary inputs such that one thermostat would be enabled and so set for normal working periods while the second thermostat would be set and enabled during off hours providing the night setback function. This selective enabling and disabling of contact closure or binary sensors are achieved by commands from the central facility means.
It is also desirable to provide a positive acknowledgement from the central facility means to the remote input transceiver verifying the action of the change of state of binary contact closures. In the prior art, a transmission would be immediately initiated by the transceiver to the central controller means upon the enabling of a binary input. Only one transmission was made such that if the central controlled means missed the message no action would take place. Since this is undesirable for use with critical inputs such as alarms, demand, security and other binary input functions, an answer back function was added. This answer back scheme would result in the input transceiver to periodically transmit to the central controller the action of the binary sensor until the reception of a positive acknowledge that the message was received from the central controller means.
It is also desirable to provide improved self diagnostics such that the central controller can detect the erroneous resetting or subsequent application of power to remotely located transceivers. This power-up and reset annunciation will insure the integrity of the distributed data base while providing a diagnostic means to trace failed devices.